U.S. patent number 4,816,205 [Application Number 07/130,591] was granted by the patent office on 1989-03-28 for remotely replaceable tokamak plasma limiter tiles.
This patent grant is currently assigned to The United States Department of Energy. Invention is credited to Gallix, Remy.
United States Patent |
4,816,205 |
|
March 28, 1989 |
Remotely replaceable tokamak plasma limiter tiles
Abstract
U-shaped limiter tiles placed end-to-end over a pair of parallel
runners secured to a wall have two rods which engage L-shaped slots
in the runners. The short receiving legs of the L-shaped slots are
perpendicular to the wall and open away from the wall, while long
retaining legs are parallel to and adjacent the wall. A sliding bar
between the runners has grooves with clips to retain the rods
pressed into receiving legs of the L-shaped slots in the runners.
Sliding the bar in the direction of retaining legs of the L-shaped
slots latches the tiles in place over the runners. Resilient
contact strips between the parallel arms of the U-shaped tiles and
the wall assure thermal and electrical contact with the wall.
Inventors: |
Gallix, Remy (San Diego,
CA) |
Assignee: |
The United States Department of
Energy (Washington, DC)
|
Family
ID: |
22445404 |
Appl.
No.: |
07/130,591 |
Filed: |
December 9, 1987 |
Current U.S.
Class: |
376/136; 376/150;
248/225.21; 211/192 |
Current CPC
Class: |
G21B
1/25 (20130101); Y02E 30/10 (20130101); Y02E
30/122 (20130101) |
Current International
Class: |
G21B
1/25 (20060101); G21B 001/00 () |
Field of
Search: |
;376/136,146,150
;248/225.2,225.1,222.1 ;211/208,103,192 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
9th Symp. on Eng. Problems of Fusion Research, Chicago, Ill., Oct.,
1981, Paper 5E-04, Winkler et al., pp. 1383-1388. .
9th Symp. on Eng. Problems of Fusion Research, Chicago, Ill., Oct.,
1981, McKelvey et al., pp. 1650-1653. .
Nuclear Technology/Fusion, vol. 4, Sep. 1983, pp. 202-207, Stacy et
al..
|
Primary Examiner: Behrend; Harvey E.
Attorney, Agent or Firm: Clouse, Jr.; Clifton E. Gaither;
Roger S. Hightower; Judson R.
Government Interests
BACKGROUND OF THE INVENTION
The invention described herein arose in the course of, or under,
Contract No. DE-AC03-84ER53158 between the United States Department
of Energy and GA Technologies, Inc.
Claims
What is claimed is:
1. In an apparatus for containing plasma in a high energy device
having walls defining a plasma chamber, at least one rail limiter
disposed on a wall within the plasma chamber, said rail limiter
consisting of a plurality of discrete tiles arranged end on end,
each tile having a uniform U-shaped cross section throughout its
length with short parallel arms and two spaced-apart transverse
rods inserted through bores in said parallel arms with a portion of
each rod exposed between said parallel arms, and means for latching
said discrete tiles on said wall comprising a pair of parallel
runners affixed to said wall, said runners being spaced from one
another sufficiently to just fit between said arms of said tiles,
and means for releasably retaining said discrete tiles on said
runners, said releasably retaining means comprising two L-shaped
slots in each runner for each tile, each of said slots having a
short leg perpendicular to the length of said runner for receiving
a rod, and a long leg parallel to said wall, each long leg of every
slot extending in the same direction for retaining a rod received
by said short leg thereof, and a sliding bar between said runners
having means for engagement with said rods in said slots to move
said tiles in a direction for forcing said rods into said long legs
of said slots.
2. Apparatus as defined in claim 1 wherein said sliding bar means
for engagement with said rods in said slots comprises a separate
transverse groove extending the width of said sliding bar for
receiving each rod, and a spring clip in each groove for retaining
each rod, whereby upon moving said sliding bar between said runners
in the direction of said long legs of said slots parallel to said
walls, each rod is forced to the end of a long leg of an associated
one of said L-shaped slots for latching said rod in place, and
thereby latching said tile in place.
3. Apparatus as defined in claim 2 wherein said long leg of each
L-shaped slot of each U-shaped tile has a surface farthest from
said wall sloped toward said wall from the entrance of said long
leg to the closed end thereof, whereby said rod is forced toward
said wall while being forced to the closed end of said long leg of
each of said L-shaped slots to assure contact with said wall by
said parallel arms of said U-shaped tile.
4. Apparatus as defined in claim 2 wherein said sliding bar extends
very nearly the full length of said runners, said bar being
slideably disposed between said runners and between said wall and
said U-shaped tiles to be received and latched, further including
taps spaced along said runners and extending over said sliding bar
to retain said sliding bar while tiles are being received and
latched, and notches in said bar, said notches being spaced along
said bar equal to the spacing of said tabs on said runners for
permitting said bar to be lifted out from between said runners
while there is no U-shaped tile with a rod in any groove of said
sliding bar.
5. Apparatus as defined in claim 3 further including a thin layer
of resilient conductive material between the ends of said parallel
arms of said U-shaped tiles and said wall, said material having
relatively high thermal and electrical conductivity, whereby
thermal contact between said tile and said wall is assured.
6. Apparatus for releasably retaining a column of U-shaped tiles on
a wall comprising
a pair of runners provided on said wall to which a discrete column
of U-shaped tiles is to be retained, said runners being spaced from
one another sufficiently to just fit between parallel arms of said
U-shaped tiles, and having at least one separate pair of slots for
each tile to be retained, one slot of a pair in each runner,
a separate rod mounted in each tile through bores in said parallel
arms of said U-shaped tile to be retained, each rod engaging a pair
of slots in said runners, said slots being L-shaped to provide a
receiving leg perpendicular to said wall and a retaining leg
parallel to said wall, and
a sliding bar having means for engaging said rod of each tile in
said slots, said engaging means being comprised of a transverse
groove for each rod to permit said receiving leg of each slot to
receive a rod to the depth of said retaining leg, whereby sliding
said bar in the direction of said retaining legs and parallel to
said wall forces said rods into said retaining legs for latching
said tiles in place.
7. Apparatus as defined in claim 6, wherein said retaining leg
extending parallel to said wall has a surface farthest away from
said wall sloped toward said wall in a direction away from said
receiving leg, whereby said rod is forced toward said wall while
being forced into said retaining leg to assure contact with said
wall.
8. Apparatus as defined in claim 7 including strips of resilient
material between said parallel sides of said U-shaped tiles and
said wall to assure thermal contact therebetween.
9. Apparatus as defined in claim 7 including spring clips disposed
in said transverse grooves of said sliding bar for releasably
gripping said rods in in said slots until said rods are latched by
sliding said bar in a direction away from receiving arms of said
slots.
10. Apparatus as defined in claim 9 wherein each of said tiles
includes two rods and said runners include two pair of slots, one
pair for each of said two rods, said two pair of slots being spaced
a distance equal to said rods in said tiles.
Description
This invention relates generally to high-energy plasma devices, and
more specifically to a means of so attaching a row of limiter tiles
to the wall of a plasma chamber that they may be individually
replaced by a suitable remote handling tool.
Plasma devices, such as Ignition Tokamak devices, require that the
walls of the chamber containing the plasma be protected from damage
by contact of the very hot plasma with the walls, while the plasma
itself needs to be protected from any contamination that may be
produced by contact with the walls. It has been proposed, as
described in U.S. Pat. No. 4,654,182, issued Mar. 31, 1987, to J.
R. D'Aoust, to use spaced rings of carbon tiles on the inside of
the plasma chamber to cause the plasma to contact only the carbon
tiles, thus reducing the heat load on the walls of the plasma
chamber while at the same time obviating metal contamination of the
plasma.
It also has been proposed to detachably connect limiter tiles to a
wall of a plasma vacuum vessel. See, for example, U.S. Pat. No.
4,619,807, issued Oct. 28th, 1986, to H. E. Kotzlowski, which
discloses the use of limiter members as a heat shield for high
thermal loading, and particularly for pulsed heat loading in fusion
reactors. The limiter members are detachably connected to a support
plate.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a system for
efficient installation and replacement of one or more discrete
elements on a supporting surface.
Another object is to provide an efficient yet reliable mechanism
for permitting installation and removal of one or more limiter
tiles in a row in a plasma chamber.
Still another object is to provide an attachment system for limiter
tiles which presses the tiles into thermal contact with the wall of
the plasma chamber for improving thermal conduction and better
cooling through channels on the other side of the wall.
These and other objects of the invention are achieved by providing
an annular plasma chamber with one or more limiters formed of a
plurality of tiles disposed end-to-end to form a ring on the inside
walls using an attachment system for releasably retaining the tiles
on the walls. The attachment system comprises a pair of runners
projecting from a chamber wall and arranged to define at least one
segment of the limiter ring. The runners are provided with spaced
L-shaped slots to receive the tiles positioned end-to-end, at least
one pair of slots for each tile to be retained end-to-end in a
rectilinear segment. The tiles are each U-shaped in cross section
throughout their length, and at least one transverse elongated
element, such as a rod, is mounted in bores through parallel arms
of the tile to be retained so as to engage the L-shaped slots of
the runners. The rod is latched in the pair of slots by a securing
system comprising a sliding bar having a groove formed therein to
receive the rod and forcing the rod into retaining legs of the
associated pair of slots by a sliding movement of the bar.
A sloped surface is preferably provided in the retaining leg of
each slot for forcing the rod of the tile being attached to be
tight against the wall of the plasma chamber as the rod is forced
along the sloped surface of the retaining leg. Thermal and
electrical contact of the tiles with the supporting wall is
enhanced by insertion of resilient conductive strips between the
back sides of the tiles and the wall. Resilient strips of beryllium
copper have been found satisfactory for this purpose.
The novel features that are considered characteristic of this
invention are set forth with particularity in the appended claims.
The invention will best be understood from the following
description when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross section at midplane looking toward an end of an
annular vacuum vessel defining a plasma chamber having six sets of
rail limiters between inner and outer vessel walls. FIG. 1a
illustrates in perspective the annular plasma vacuum vessel of FIG.
1.
FIG. 2 is a perspective view showing one set of rail limiters as
used in the vacuum vessel of FIG. 1.
FIG. 3a is a fragmentary, perspective view, partially cut away and
in section, showing a preferred rail limiter tile and attachment
system according to the present invention. FIG. 3b is a partially
exploded view of FIG. 3a, and FIG. 3c illustrates schematically a
simple manipulator for removing and replacing a rail limiter tile
from a wall once the tiles in a row are unlatched.
FIG. 4 is a fragmentary, cross-sectional view taken generally along
the line 4--4 of FIG. 3.
FIG. 5 is an enlarged, fragmentary, cross-sectional view taken
generally along the line 5--5 of FIG. 4.
FIG. 6 is an enlarged, fragmentary, side-elevational view showing a
detail of the attachment system of FIGS. 3 through 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, an annular plasma chamber 10 having an inner
wall 11 and an outer wall 12 is protected from contact with a
plasma in a region between the walls by, for example, six sets of
rail limiters 13 in the form, shown in FIG. 2, of four straight
subsets of rail limiters 14, 15, 16 and 17. Each set of rail
limiters surrounds the plasma region in a rectangular frame when
thus arranged on the walls of the chamber 10.
The plasma chamber in this preferred embodiment has a rectangular
cross section because its inner and outer walls are hollow
cylinders, as shown in FIG. 1a. But the chamber may have other
cross sections, such as circular or D-shape, for example. The sets
of rail limiters would then be arranged in a circular or D
shape.
The rail limiters 14, 15, 16 and 17 are made up of a plurality of
individual tiles 18, such as eight shown in FIG. 2 for a subset of
tiles that are arranged end-to-end on the inner wall 11, or other
wall 12. The rail limiters on the end walls 19a and 19b are made up
of fewer tiles, for example, the two shown in FIG. 2. The total
distance D, or build of each limiter shown in FIG. 1 can be, for
example, about 50 mm for a rail limiter 120 mm wide and 160 mm
long. The chamber walls (sides and ends) receive about 50% of the
heat load; the rail limiters receive the rest of the heat load.
As the plasms moves circularly in the chamber under the influence
of electromagnetic forces (not shown), it passes through one rail
limiter after another. As it leaves one set, it will tend to
expand, but not at a sufficient rate to impinge the walls before
reaching the next set of rail limiters. There the plasma that might
otherwise tend to reach the walls will strike the limiters. Cooling
channels 20 are spaced around the inside of the inner wall 11.
Cooling channels for the outer wall are provided by implementing
the outer wall with two concentric hollow cylinders 12a and 12b
with spacers between them in an arrangement analogous to the manner
in which corrugated cardboard is made.
The tiles 18 are preferably constructed from graphite, or other
suitable material providing a low atomic number contact surface to
a plasma contained in the chamber 10. Graphite is preferred because
it is also quite resistant to thermal shock and high
temperature.
In accordance with the present invention, the limiter tiles 18 are
attached to a wall by a quick-disconnect system 20 illustrated in
FIGS. 3 through 6 for attachment to a wall, such as the inner wall
11. The only difference between the parts of the quick-disconnect
system for the outer wall 12, or an end wall, is simply conforming
the parts for an interface with a convex or flatwall instead of
concave wall.
The quick-disconnect system allows a simple manipulator shown
schematically in FIG. 3c to individually remove and replace damaged
tiles 18. Each tile is U-shaped in cross section throughout its
length, and has two transverse elongated elements, such as rods 21,
inserted through bores 22 near the two end surfaces 23 of the arms
of the U-shaped tile 18. (See FIG. 3b and FIG. 4.) A portion, or
length, of each rod 21 is exposed between the parallel arms of the
tile. Two fixed parallel runners 25 and 26 provided with L-shaped
slots 27 (FIG. 3a) are attached to the chamber wall 11, such as by
welding, over the full length of the rail limiter. The tiles 18 are
then attached to the runners by forcing their associated rods 21
into the runner slots 27. (See FIG. 3a.) A single bar 28 sliding
between the runners 25 and 26 has almost the same length as the
associated rail limiter, and is provided with transverse grooves 29
spaced along the full length of the sliding bar 28 the same
distances apart as the slots 27 in the runners 25 and 26.
To install the tiles 18, the sliding bar 28 is first positioned
with its grooves 29 aligned with the openings of the slots 27
provided in the runners 25 and 26. Each tile 18, which weighs only
about 4 lbs., for example, is grappled with a remote manipulator,
such as that shown in FIG. 3c. It has two pair of tongs a and b
held in a "closed" position as shown by springs c and d. The
"closed" position is determined by stops on solenoids e and f,
respectively. When the solenoids are energized electrically by
closing a switch S, the solenoids force armatures out to open the
ends of the respective tongs, thus separating the tongs
sufficiently to fit over the bores 22 for the rods 21. By opening
the switch S, the ends of the tongs are allowed to close into the
bores 22 against the rods 21. (The rods may be hollow tubes to
permit the ends of the tongs to enter their ends, and not just the
bores 22 of the tile.) The manipulator may then be used to remove
the tile or to place a new tile in the sliding bar grooves 29 and
the aligned L-shaped slots 27 in the runners. Once the tile is in
place, the switch S is again closed to open the tongs and remove
the manipulator. The manipulator is inserted into or withdrawn from
the chamber 12 through an open end, or a port (not shown) in the
end.
When a tile 18 is installed over grooves 29 in the sliding bar 28
aligned with slots 27 in the runners 25 and 26, spring clips 30
(FIG. 6) retain the rods. The spring clips are in turn retained by
screws 31. There is one spring clip 30 in each groove 29 extending
the full width of the sliding bar 28. In that manner, a rod 21 of a
tile 18 is retained in place after it is released by the
manipulator, until the slide bar 28 is moved to the latching
position shown in FIGS. 3a and 5.
When all of the tiles 18 have been installed on runners 25 and 26
for a given one of the rail limiters as described above, the tiles
18 are locked in place simultaneously by sliding the bar 29 a short
distance in the direction of the downward arrow in FIG. 3a until
the upper sides of the grooves 29 (as shown in FIG. 6) of the bar
28 push the rods 21 into retaining legs 27" of the runner slots 27
as shown in FIG. 3b. The runner slots have sloped surfaces or ramps
in the retaining legs disposed at an angle of, for example,
4.degree. to opposed surfaces at the back of the slots as indicated
in FIG. 5, which force the tiles 18 back into contact with
resilient conductive strips 32 (e.g., beryllium copper) against the
chamber wall 11. This secures tiles 18 in place with good thermal
and electrical conductance to the wall.
To replace any tile 18 of a rail limiter, the sliding bar 28 is
pulled in the direction of the upward arrow in FIG. 3, unlocking
all tiles 18 and freeing rods 21 from the runner slots 27 so the
tiles 18 can be removed and replaced, one at a time, in any order,
preferably by a suitable manipulator such as that shown in FIG. 3c,
which allows manipulation from a remote position outside the
chamber, although, before the vessel 10 becomes contaminated, it
can be entered to replace the tiles by hand. Space allowance is
made at both ends of a rail limiter (as shown in FIG. 3a) to
accommodate the slight movement of the sliding bar 28 and
associated tiles 18 during the latching and unlatching
operations.
It should be noted that bar retaining tabs 33 shown in FIG. 3b on
the runners 25 and 26 are spaced to hold the bar in place during
normal unlatching of the tiles to replace one or more of them. To
be able to easly remove the bar when all of the tiles have been
removed, notches 34 are spaced along the length of the bar 28 so
that by aligning the notches 34 with the tabs 33, the bar may be
lifted out from between the runners by pulling it away from the
wall. The clips 30 which extend the width of the bar may be used to
engage the bar 28 by a suitable manipulator to accomplish this.
The rail limiter system described is sized to resist vibrations and
electromagnetic loads placed on the system by disruptions of the
plasma in the annular region of the chamber 10. During a full power
D-T shot, for example, the limiter surface heat load of a model
having four-foot limiters 14 and 16 was approximately one-half of
the ohmic power deposited in the plasma (61 MJ in 15 sec) plus
one-half of the alpha-particle power (102 MJ in 5 sec). A 10 mm
plasma scrape-off length is assumed, resulting in a 5.8 MW/cm.sup.2
peak power loading on the tiles. There is also volume heating in
the limiters due to neutron and radiation (.about.22 W/cm.sup.2 for
5 sec). Assuming that the heat load is uniform along all six sets
of rail limiters, the maximum tile temperature rise will be about
1500.degree. C. at the end of a 15 sec shot. The maximum tensile
and compressive thermal stresses are slightly less than 40% of the
respective ultimate strengths. The heat deposited on the limiters
during the shot is first stored inertially in the tiles. It is then
transferred by conduction to the chamber wall and carried away by a
chamber coolant in channels 20 (FIG. 4) before the next shot. To
improve thermal and electrical conductance between the tiles and
wall, beryllium copper strips 32 are placed between the back side
(interface) of the tiles 18 and the vessel wall. The tiles return
to their initial temperature in about 15 minutes after each full
power shot.
Although particular embodiments of the invention have been
described and illustrated herein, it is recognized that
modifications and variations may readily occur to those skilled in
the art. Consequently, it is intended that the claims be
interpreted to cover such modifications and variations.
* * * * *